Functional significance of laser-evoked potentials (LEPs)

14/02/2010 15:11

Laser stimuli activate selectively pain-related afferents in the skin, and evoke brain responses that can be detected by EEG (laser-evoked potentials, LEPs). Despite being widely used, the functional significance of LEPs is still unclear. When single laser stimuli are delivered, the magnitude of the elicited brain response allows us to predict the amount of pain that a subject feels. However, we observed that when laser stimuli are repeated the intensity of pain is unchanged, but the LEP amplitude is reduced (see Iannetti et al 2008). So, it seems that LEPs do not always reflect the amount of pain we perceive. Why are LEPs modulated by repeated stimulation? What do they reflect? Is there a part of them specifically reflecting pain perception? Why do we have an LEP (at all)? A series of experiments are underway to address these questions, by changing some physical features within a sequence of repeated stimulation.